<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <!-- <script>
        function User(name, pass) {
            this.name = name;
            this.pass = pass;
        }

        User.prototype.showName = function() {
            alert(this.name);
        }
        User.prototype.showPass = function() {
            alert(this.pass);
        }

        function VipUser(name, pass, level) {
            User.call(this, name, pass);
            this.level = level;
        }

        VipUser.prototype = new User();
        VipUser.prototype.constructor = VipUser;

        VipUser.prototype.showLevel = function() {
            alert(this.level);
        }

        var v1 = new VipUser('Horace', '123456', 3);

        v1.showName();
        v1.showPass();
        v1.showLevel();
    </script> -->

    <script>
        class User {
            constructor(name, pass) {
                this.name = name;
                this.pass = pass;
            }

            showName() {
                alert(this.name);
            }

            showPass() {
                alert(this.pass);
            }
        }

        class VipUser extends User {
            constructor(name, pass, level) {
                super(name, pass);
                this.level = level;
            }

            showLevel() {
                alert(this.level);
            }
        }

        var v1 = new VipUser('Horace', '123456', 3);

        v1.showName();
        v1.showPass();
        v1.showLevel();
    </script>
</body>

</html>